It is a problem to reliably and acurately monitor the position of a human body during various activities. For example, is important for athletes to monitor and maintain proper body position while performing or training for athletic events. In the game of tennis, it is particularly important for the tennis player to keep his or her head in what is known as a "head-up" position, not only when approaching the ball, but also while stroking the ball with the racquet. Professional tennis players recognize that maintaining a proper head-up position is a key factor in perfecting one's proficiency in the game. It is a problem to provide the tennis player or tennis coach with visual or audible cues to indicate that the player's head is in the proper head-up position.
Numerous systems are known in the prior art for indicating a player's head position during sports activities. However, the known systems generally require substantial set-up in order to operate properly. Furthermore, the known systems generally are best suited for sports activities where the player's body is in a relative static position, and head movement is relatively infrequent, and the head position is only critical for a short period of time.
For example, a number training systems are known for golf players which give an indication if the golf player lifts his head head prematurely during a golf swing. That is, the device mounted on the golf player's head simply gives an alarm when it senses any movement of the head.
The game of tennis, unlike golf, requires that the player moves rapidly on the court, frequently shifting body position, with sudden stops and starts, while responding to the celeritous movement of the tennis ball. As the player moves, the head is likely to bob up, down, and sideways with relative frequency, and thus, known training systems would too often give erroneous positional information, making them difficult and annoying to use.
Therefore, there is a need for a training system which can reliably monitor and indicate head positions while the tennis player moves on the court. Furthermore, it is desirable that such a system be simple to operate while giving the player and the coach accurate positional information.